The present invention relates to a method for the measurement of a consumable electrode and in particular to the use of a laser to measure the consumption of the electrode paste and the electrode casing of a consumable electrode in an electric arc melting furnace.
In one particular embodiment, a laser measuring means is mounted on a crane traveller above the operating electrodes, to allow for sequential measurement of more than one variable in each of a number of energised electrodes.
In a further embodiment, the present invention also relates to computer data processing and storage means capable of calculating data based upon the measurement data obtained from the laser measuring means. In particular, the computer data processing and storage means calculates the solid and liquid carbon paste heights, electrode casing height and the operating length of the electrode from the data obtained from the laser measuring means.
In the Ferro Nickel industry, selected ore types containing the oxides of iron, nickel, silica and magnesium are first treated in a roaster under reducing conditions to convert the oxides of iron and nickel to metallic species. This reduced matrix is then subjected to high temperatures produced in an electric arc furnace to coalesce the metal particles and form molten metal which is removed from the furnace base, cooled and usually granulated. The electric arc is struck between a graphite electrode and the molten metal. The graphite electrode may typically be about 1.8 meters in diameter. During this process, the electrode is eroded and consumed and requires continual renewing external to the furnace to maintain its operating length. This renewal is achieved by adding blocks of solid carbon paste, which liquefy when heated and then, as the electrode mass moves into the furnace, it is exposed to high temperatures and bakes solid. The baked electrode solid adheres strongly to the metal casing of the electrode so that pneumatic movement up and down of the casing changes the position of the electrode tip. It is the instantaneous length of the electrode relative to the molten metal in the furnace which has to be controlled to ensure stability of the electric arc length.
To ensure that the furnace functions correctly, the levels of electrode paste, namely the solid and liquid paste, and the electrode casing consumption are measured regularly. These variables have been measured manually in the past, however due to safety hazards involved, manual measurement was discontinued and measurement could only be achieved when the furnace was de-energised every three to four weeks for casing renewal and maintenance.
This length of time between measurements compromised the operating efficiency of the furnace because levels of solid and liquid paste should be determined regularly in order to control addition of paste to the electrode casing and operation of resistance heating of the paste.
While the need to monitor instantaneous electrode length including the solid and liquid paste levels has long been recognised, little attention has been given to electrode paste and electrode casing height measurements.
U.S. Pat. No. 4,834,234 summarises various techniques for measurement of a carbon electrode. This US patent describes a method using optical means (optical time domain reflectometry) which determines the position of the electrode tip within an arc furnace by incorporation of a fibre optic cable into the carbon electrode. This requires a physical connection between the measuring device and the electrode and does not address the measurement of levels of liquid and solid paste in the electrode casing or the consumption rate of the casing housing the electrode.
The above discussion of documents, acts, materials, devices and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these materials form part of the prior art base or the common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.
The present invention aims to overcome or at least alleviate one or more of the difficulties associated with the prior art as indicated above.